Characterising the new DLR cryogenic reflectance spectroscopy facility for outer planets exploration

Kurzfassung

Exploring the outer solar system is a priority, with upcoming missions including ESA JUICE and NASA Europa Clipper and Lucy missions. Spectroscopic analyses under extraterrestrial conditions are highly relevant in space science business. To meet this demand, PSL has added a compact low-temperature vacuum chamber for bi-directional reflectance measurements that attaches directly to an existing spectrometer. In this chamber, rock samples are examined in a high vacuum at temperatures of down to -200°C. In this cryo-chamber, solar radiation on asteroids and moons will be simulated in order to gain insights into their spectral properties. Initial functional tests showed that the heat transfer between the cooling system and the sample cylinder did not produce satisfactory results, since temperatures below -150°C could not be reliably achieved and cooling times were long. Subsequent work was dedicated to optimizing the heat transfer in the cooling system, consisting of a Stirling cooler, cooling block and sample cylinder. As a result of these improvements temperatures of down to -200°C and significantly shorter cooling and warming times can be achieved. The updated system allows for measurements from UV to far infrared and includes a two-stage turbo vacuum pump, a glove box for preparing icy samples, and an airlock for loading samples while maintaining high vacuum.